Mortality rates and cause of mortality in patients with mildly elevated pulmonary pressures versus PH: insights from the retrospective EVIDENCE-PAH study

Background

Normal mean pulmonary artery pressure (mPAP) does not exceed 20 mmHg and normal pulmonary vascular resistance (PVR) does not exceed 2 Wood Units (WU). The thresholds used to define pre-capillary pulmonary hypertension (PH) – mPAP ≥25 mmHg and PVR >3 WU – are being evaluated. It is unclear if treatment would benefit patients with mildly elevated mPAP (≥21–<25 mmHg).

Purpose

The EVIDENCE-PAH study aims to describe mortality and hospitalisation outcomes, clinical characteristics, therapies, and quality of life during long-term follow-up of a national cohort of patients with different levels of mPAP and PVR. We report preliminary analyses focusing on mortality and its cause in patients stratified by their baseline (BL) mPAP.

Methods

This retrospective analysis included PAH-treatment-naïve patients with suspected PH who received a first right heart catheterisation (RHC) between 2009 and 2017 at any of the 7 UK tertiary PH centres, which assess all PH patients in the UK. A sample of patients with BL mPAP ≥25 mmHg (stratified by PVR and treatable versus non-treatable PH) was used as a control in this analysis. Baseline characteristics, mortality and cause of mortality were stratified by mPAP (<21, ≥21–<25, ≥25 mmHg) at BL (first RHC). Mortality was also stratified by BL PVR (<1, 1–<2, 2–<3, 3–<6, ≥6 WU). Mortality analysis was done without matching cohorts. Mortality data were obtained from the Office for National Statistics, NHS Digital.

Results

In total, 2926 patients were analysed (968, 689 and 1269 with mPAP <21, ≥21–<25, ≥25 mmHg, respectively). Mean observation was 6.1 years. BL characteristics are in Table. Survival worsened with increasing mPAP (p<0.0001) and increasing PVR (p<0.01) (Figure). After 5 years of follow-up, 187 (27.1%) patients with mPAP ≥21–<25 mmHg had died, compared with 162 (16.7%) and 595 (46.9%) patients in the lower and higher mPAP groups, respectively. In patients with mPAP ≥21–<25 mmHg, the most common main cause of death was respiratory disease (36.4%) – with scleroderma lung disease and interstitial lung disease accounting for 69.1% of these deaths – followed by cardiac disease (16.6%) and malignancy (15.0%) (Table). PH was the main cause of death for only 1.6% of patients with mildly elevated mPAP and it was a contributor to death in 6.8% (BL mPAP <21 mmHg), 10.2% (≥21–<25 mmHg), and 40.2% (≥25 mmHg) of cases.

Conclusion

Long-term survival in patients with mPAP ≥21–<25 mmHg was worse than in those with normal mPAP, and better than in those with the current definition of PH. While the main cause of death was mostly unrelated to PH and further analysis is needed to understand the impact of underlying disease, mildly elevated mPAP appears to confer a worse prognosis and should be closely monitored. These data show the relevant disease burden in patients with mPAP ≥21–<25 mmHg and the need to understand if they could benefit from treatment. PVR may be key in determining patients who might benefit.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Actelion Pharmaceuticals Ltd., a Janssen pharmaceutical company of Johnson & Johnson.

Concomitant initiation of combination therapy with macitentan and tadalafil in pulmonary arterial hypertension (PAH) patients with comorbidities: real-world data from OPUS and OrPHeUS

Background

Guidelines for the management of pulmonary arterial hypertension (PAH) recommend early combination therapy of an endothelial receptor antagonist (ERA) and a phosphodiesterase type-5 inhibitor (PDE5i) [1]. There is, however, limited guidance about the management of PAH patients with comorbidities.

Purpose

To describe the demographics, clinical characteristics, safety, tolerability, and outcomes associated with initiation of the ERA macitentan and the PDE5i tadalafil in patients with comorbidities in the US OPsumit® USers (OPUS) and the OPsumit® Historical USers cohort (OrPHeUS) combined dataset.

Methods

This analysis reports data from the OPUS registry (Apr 2014–Jun 2020) and OrPHeUS medical chart review (Oct 2013–Mar 2017) on PAH patients initiating macitentan and tadalafil (M+T) combination therapy, in any order, as concomitant initiation (≤60 days apart, concomitant initiation group). The index date was defined as the start date of the second therapy (i.e., the start of combination therapy). Patients were further grouped by the number of comorbidities present prior to or at macitentan initiation: systemic hypertension, diabetes, renal insufficiency, BMI ≥30 kg/m2, other signs of right heart failure and atrial fibrillation. Results are presented descriptively alongside results for all PAH patients receiving M+T combination therapy (overall M+T group).

Results

Of the 1336 PAH patients that received M+T combination therapy, 431 (32%) were in the concomitant initiation group. In the concomitant initiation and overall M+T groups, respectively: 72% and 68% had ≥1 comorbidity, and the most common were systemic hypertension (47% and 47%), obesity (32% and 26%) and diabetes (23% and 22%). Patients were more likely to be older, male and have idiopathic/heritable PAH with increasing comorbidity burden (Table 1). Patients in the concomitant initiation group were more likely to be incident (median time from diagnosis: 1–2 months vs 9–24 months in the overall M+T group; Table 1). Most patients had ≥1 adverse event (AE); in both groups, patients with a high comorbidity burden (≥3) were more likely to have had an AE and to have discontinued treatment (Table 2). The incidence rate of first all-cause hospitalisation and mortality by comorbidity was comparable between the concomitant initiation and overall M+T groups.

Conclusions

In the real-world, concomitant initiation of M+T is used in PAH patients with comorbidities, usually shortly after diagnosis. Patient characteristics were similar for the concomitant initiation and overall M+T groups, with the exception of time from diagnosis. At index date, age, gender proportion, and PAH aetiology differed between the comorbidity groups. The safety profile of M+T combination therapy in the concomitant initiation group was consistent with that in the overall M+T group.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): Actelion Pharmaceuticals Ltd, a Janssen Pharmaceutical Company of Johnson & Johnson

Cardiac biomarkers as prognosticators among SARS-CoV-19 patients in a tertiary hospital in Philippines

Background

There is overwhelming volume of confirmed cases of COVID-19, despite this numerous knowledge gaps remain in the diagnosis, management, and prognostication of this novel coronavirus infection, making prevention and control a challenge.

Methods

This retrospective cohort study included patients with real-time reverse transcriptase polymerase chain reaction (rRT-PCR)-confirmed COVID-19. Binary logistic regression was used to determine the association between the cardiac biomarkers and in-hospital mortality. ROC, AUC, and cutoff analyses were used to determine optimal cutoff values for the cardiac biomarkers.

Results

A total of 90 subjects with a complete panel of cardiac biomarkers out of the 224 rRT-PCR confirmed cases were included. The median age was 57 years (IQR, 47–67 years), majority were males. Sixty-six (77.6%) subjects survived while 19 (22.4%) expired. The most common presenting symptom was fever (75.6%), and the most common comorbidity was hypertension (67.8%). Spearman rho correlation analysis showed moderate positive association of high sensitivity troponin I (hsTnI) with in-hospital mortality (R, 0.434, p = <0.001). Multivariate binary logistic regression analysis showed that creatine kinase and hsTnI were independently associated with in-hospital mortality (OR, 4.103 [95% CI, 1.241–13.563], p=0.021; and OR, 7.899 [95% CI, 2.430–25.675], p=0.001, respectively). ROC curve analysis showed that hsTnI was a good predictor for in-hospital mortality (AUC, 0.829 [95% CI, 0.735–0.923], p = <0.001) and that creatine kinase was a poor predictor (AUC, 0.677 [95% CI, 0.531–0.823], p=0.018). Optimal cutoff point derived from the ROC curve for hsTnI was 0.010 ng/ml (J, 0.574) with a sensitivity of 84% (TPR, 0.842 [95% CI, 0.604–0.966]), specificity of 73% (TNR, 0.732 [95% CI, 0.614–0.386]), and an adjusted negative predictive value of 99% (Known prevalence*adjusted NPV, 0.989), a positive likelihood ratio of 20% (LR+, 3.147 [95% CI, 2.044–4.844]) and a negative likelihood ratio of 30% (LR−, 0.216 [95% CI, 0.076–0.615]).

Conclusion

High sensitivity troponin I level was a good tool with a very high negative predictive value in significantly predicting in-hospital mortality among rRT-PCR positive COVID-19 patients.

Funding Acknowledgement

Type of funding sources: None.

Treatment with macitentan for pulmonary arterial hypertension (PAH) associated with congenital heart disease (CHD): real-world experience from the combined OPUS and OrPHeUS data sets

Introduction

Restrictive inclusion criteria can exclude some CHD-PAH patients from clinical trials. The OPsumit® USers (OPUS) Registry and the OPsumit® Historical USers (OrPHeUS) data sets provide real-world data in PAH patients newly started on macitentan, including patients with CHD-PAH regardless of defect type.

Purpose

To describe the characteristics, safety and clinical outcomes of CHD-PAH patients newly treated with macitentan.

Methods

OPUS is a prospective, US, multicentre, observational drug registry ongoing since April 2014. OrPHeUS was a retrospective, US, multicentre chart review; observation period Oct 2013–Mar 2017. This analysis reports information on CHD-PAH patients in the combined OPUS/OrPHeUS data set, descriptively compared with idiopathic/heritable PAH (I/HPAH) patients.

Results

As of Sept 2019, there were 4268 PAH patients with follow-up data, of whom 264 (6%) had CHD-PAH and 2396 (56%) had I/HPAH. For CHD-PAH and I/HPAH patients respectively at macitentan initiation: median age (Q1, Q3) was 48 (36, 62) and 65 (53, 73) years; 199 (75%) and 1748 (73%) were female; 67/114 (59%) and 802/1301 (62%) were WHO functional class III/IV; median (Q1, Q3) 6-minute walk distances were 350 (274, 420) and 289 (195, 375) m for the 82 and 840 patients with measurements; median (Q1, Q3) time from PAH diagnosis to macitentan initiation was 37.3 (4.5, 113.1) and 7.4 (1.4, 38.3) months; and 99 (38%) and 1056 (44%) initiated macitentan as monotherapy. The number of patients with ≥1 hepatic adverse event (HAE) was similar for CHD-PAH and I/HPAH (22 [8%] and 184 [8%]), as were the adverse event (AE) profiles (collected from OPUS only). Exposure, discontinuations, outcomes and most common AEs are shown in the table.

Conclusions

In general, compared with I/HPAH patients, CHD-PAH patients were younger and a greater proportion had prevalent disease than I/HPAH patients. Safety and outcomes were similar between the groups.

Funding Acknowledgement

Type of funding source: Other. Main funding source(s): Actelion Pharmaceuticals Ltd

Variants in ACTG2 underlie a substantial number of Australasian patients with primary chronic intestinal pseudo-obstruction

BACKGROUND

Primary chronic intestinal pseudo-obstruction (CIPO) is a rare, potentially life-threatening disorder characterized by severely impaired gastrointestinal motility. The objective of this study was to examine the contribution of ACTG2, LMOD1, MYH11, and MYLK mutations in an Australasian cohort of patients with a diagnosis of primary CIPO associated with visceral myopathy.

METHODS

Pediatric and adult patients with primary CIPO and suspected visceral myopathy were recruited from across Australia and New Zealand. Sanger sequencing of the genes encoding enteric gamma-actin (ACTG2) and smooth muscle leiomodin (LMOD1) was performed on DNA from patients, and their relatives, where available. MYH11 and MYLK were screened by next-generation sequencing.

KEY RESULTS

We identified heterozygous missense variants in ACTG2 in 7 of 17 families (~41%) diagnosed with CIPO and its associated conditions. We also identified a previously unpublished missense mutation (c.443C>T, p.Arg148Leu) in one family. One case presented with megacystis-microcolon-intestinal hypoperistalsis syndrome in utero with subsequent termination of pregnancy at 28 weeks' gestation. All of the substitutions identified occurred at arginine residues. No likely pathogenic variants in LMOD1, MYH11, or MYLK were identified within our cohort.

CONCLUSIONS AND INFERENCES

ACTG2 mutations represent a significant underlying cause of primary CIPO with visceral myopathy and associated phenotypes in Australasian patients. Thus, ACTG2 sequencing should be considered in cases presenting with hypoperistalsis phenotypes with suspected visceral myopathy. It is likely that variants in other genes encoding enteric smooth muscle contractile proteins will contribute further to the genetic heterogeneity of hypoperistalsis phenotypes.

TPM3 deletions cause a hypercontractile congenital muscle stiffness phenotype

OBJECTIVE

Mutations in TPM3, encoding Tpm3.12, cause a clinically and histopathologically diverse group of myopathies characterized by muscle weakness. We report two patients with novel de novo Tpm3.12 single glutamic acid deletions at positions ΔE218 and ΔE224, resulting in a significant hypercontractile phenotype with congenital muscle stiffness, rather than weakness, and respiratory failure in one patient.

METHODS

The effect of the Tpm3.12 deletions on the contractile properties in dissected patient myofibers was measured. We used quantitative in vitro motility assay to measure Ca(2+) sensitivity of thin filaments reconstituted with recombinant Tpm3.12 ΔE218 and ΔE224.

RESULTS

Contractility studies on permeabilized myofibers demonstrated reduced maximal active tension from both patients with increased Ca(2+) sensitivity and altered cross-bridge cycling kinetics in ΔE224 fibers. In vitro motility studies showed a two-fold increase in Ca(2+) sensitivity of the fraction of filaments motile and the filament sliding velocity concentrations for both mutations.

INTERPRETATION

These data indicate that Tpm3.12 deletions ΔE218 and ΔE224 result in increased Ca(2+) sensitivity of the troponin-tropomyosin complex, resulting in abnormally active interaction of the actin and myosin complex. Both mutations are located in the charged motifs of the actin-binding residues of tropomyosin 3, thus disrupting the electrostatic interactions that facilitate accurate tropomyosin binding with actin necessary to prevent the on-state. The mutations destabilize the off-state and result in excessively sensitized excitation-contraction coupling of the contractile apparatus. This work expands the phenotypic spectrum of TPM3-related disease and provides insights into the pathophysiological mechanisms of the actin-tropomyosin complex.

Comparing the efficacy of sunitinib with sorafenib in xenograft models of human hepatocellular carcinoma: mechanistic explanation

Hepatocellular carcinoma (HCC) is the fifth most common and third deadliest malignancy. Sorafenib has demonstrated 44% survival advantage over placebo and has emerged as a standard of care in advanced HCC. The therapeutic effects of sorafenib are however transient and hence additional treatment options are warranted. In this study, we aimed to compare the efficacy of sunitinib relative to sorafenib, two potent inhibitors of protein tyrosine kinases involved in tumor growth, metastasis, or angiogenesis. We reported that sorafenib and sunitinib suppressed tumor growth, angiogenesis, cell proliferation, and induced apoptosis in both orthotopic and ectopic models of HCC. However, the antitumor effect of 50 mg/kg sorafenib was greater than that of 40 mg/kg sunitinib. Sorafenib inhibited p-eIF4E Ser209, p-p38 Thr180/Tyr182 and reduced survivin expression. This was not seen with sunitinib. In addition, the antitumor and apoptotic effects of sorafenib, which are associated with upregulation of fast migrating Bim and ASK1 and downregulation of survivin, were greater than that of sunitinib. These observations explained in part the apparent superior anti-tumor activity of sorafenib compared to sunitinib. In conclusion, sunitinib demonstrated an inferior anti-tumor activity compared to sorafenib in ectopic and orthotopic models of human HCC. It remains to be seen whether such observations would be recapitulated in humans.

Validation of hyperbaric oxygen treatment software for use with monoplace chambers

Hyperbaric oxygen (HBO2) therapy is increasingly used in the treatment of a wide variety of medical conditions. However, for monoplace chambers, there is some uncertainty when sufficiently high oxygen concentrations are attained, because most chambers are not instrumented to measure oxygen. To remedy this, Microsoft Excel-based software, HBO O2 Smart Guide, was developed to simulate the atmosphere ofmonoplace chambers during treatment. Based upon chamber dimensions, patient weight, oxygen purge rates, desired pressurization, and HBO2 time, the program calculates oxygen concentration, consumption and exposure for each treatment. Software testing was conducted using four different chambers instrumented with an oxygen analyzer. Two purge rate profiles were used: constant, and biphasic (a high initial purge rate was changed to a lower plateau rate when pressurization was reached). Comparison of measured and calculated times to reach 95% oxygen concentration within the chambers demonstrated the software was accurate within 1%. The HBO O2 Smart Guide enables optimum purge profiles to be simulated with resultant potential improvements in HBO2 treatment efficacy, calculation of effective oxygen exposures (actual time during prescribed treatment during which patient breathes > or = 95% oxygen) to enable more accurate comparison of treatment profiles and outcomes, and cost savings in oxygen usage. This software will enable clinicians to provide more consistent HBO2 treatments.

Injury risk factors among telemark skiers

We performed a population survey of telemark skiers over two ski seasons to determine specific risk factors for injury. The survey inquired about the skier's sex, experience, equipment used, injuries, and number of days skied in each season. The respondents completed the surveys whether or not they were injured while skiing. We received 677 responses from telemark skiing clubs, with 19,962 skier-days of data. The number of self-reported injuries was 178, for an overall self-reported injury rate of 8.9 per 1000 skier-days. Knee injuries (N = 48) were the most common injury (27%), followed by thumb (N = 32, 18%) and shoulder (N = 21, 12%) injuries. Specific risk factors for injury were identified with multivariate regression and survival analysis. The skill level of the skier had a significant injury-sparing effect, as did the use of plastic telemark boots. The protective effect of the plastic boots was likely due to the increased stability they provided compared with traditional leather boots. There were fewer knee injuries with the recently available releasable bindings for telemark skis. Sex and age had no significant impact on injury rates in this study population. As all reported deaths associated with telemark sking were due to environmental hazards, skiers must continue to pay close attention to these hazards in the backcountry.

Effect of cAMP elevating agents on carbachol-induced phosphoinositide hydrolysis and calcium mobilization in cultured canine tracheal smooth muscle cells

The effects of increases in intracellular adenosine 3',5'-cyclic monophosphate (cAMP) on carbachol-induced generation of inositol phosphates (IPs) and increases in intracellular Ca2+ ([Ca2+]i) were investigated in canine cultured tracheal smooth muscle cells (TSMCs). The cAMP elevating agents, cholera toxin (CTX) and forskolin, induced concentration- and time-dependent cAMP formation with half-maximal effects (-logEC50) at concentrations of 7.6 +/- 1.3 g/ml and 4.8 +/- 0.9 M, respectively. Forskolin caused a concentration-dependent inhibition of carbachol-induced increase in [Ca2+]i with half-maximal inhibition (-logEC50) at 5.2 +/- 0.7 M. Pretreatment of TSMCs with either CTX (10 micrograms/ml, 4 h), forskolin (10-100 microM, 30 min), or dibutyryl cAMP (1 mM, 30 min) inhibited carbachol-stimulated Ca2+ mobilization and IPs accumulation. The inhibitory effects of these agents produced both depression of the maximal response and a shift to the right of the concentration-response curve of carbachol without changing the EC50 values. After treatment with forskolin for 24 h, carbachol-induced IPs accumulation and Ca2+ mobilization were close to those of control group. SQ-22536 [9-(tetrahydro-2-furanyl)-9H-purin-6-amine, 10 microM], an inhibitor of adenylate cyclase, and HA-1004 [N-(2-guanidinoethyl)-5-isoquinolinesulfonamide hydrochloride, 50 microM], an inhibitor of cAMP-dependent protein kinase (PKA), attenuated the ability of forskolin to inhibit carbachol-induced IPs accumulation. Moreover, the inactive analogue of forskolin, 1,9-dideoxy forskolin, did not inhibit these responses evoked by carbachol, suggesting that activation of cAMP/PKA was involved in these inhibitory effects of forskolin. The KD and Bmax values of the muscarinic receptor (mAChR) for [3H]-N-methyl scopolamine binding were not significantly changed by forskolin treatment for 30 min and 24 h, suggesting that the inhibitory effect of forskolin is distal to the mAChR. The locus of this inhibition was further investigated by examining the effect of forskolin treatment on AIF4(-)-stimulated IPs accumulation in canine TSMCs. The AIF4(-)-induced response was inhibited by forskolin, supporting the notion that G protein(s) are directly activated by AIF4- and uncoupled to phospholipase C by forskolin treatment. We conclude that cAMP elevating agents inhibit carbachol-stimulated generation of IPs and Ca2+ mobilization in canine cultured TSMCs. Since generation of IPs and increases in [Ca2+]i are very early events in the activation of mAChRs, attenuation of these events by cAMP elevating agents might well contribute to the inhibitory effect of cAMP on tracheal smooth muscle formation.

Inhibitory effect of phorbol ester on bradykinin-induced phosphoinositide hydrolysis and calcium mobilization in cultured canine tracheal smooth muscle cells

Regulation of the increase in inositol 1,4,5-trisphosphate (IP3) production and intracellular Ca2+ concentration ([Ca2+]i) by protein kinase C (PKC) was investigated in cultured canine tracheal smooth muscle cells (TSMCs). Stimulation of TSMCs by bradykinin (BK) led to IP3 formation and caused an initial transient peak followed by a sustained elevation of [Ca2+]i in a concentration-dependent manner. Pretreatment of TSMCs with phorbol 12-myristate 13-acetate (PMA, 1 microM) for 30 min blocked the BK-induced IP3 formation and Ca2+ mobilization. However, this inhibition was reduced after incubating the cells for 4 h with PMA. Inactive phorbol ester, 4 alpha-phorbol 12,13-didecanoate at 1 microM, did not inhibit these responses to BK. Prior treatment with staurosporine (1 microM), a PKC inhibitor, inhibited the effect of PMA on the BK-induced response, suggesting that the effect of PMA is mediated by the activation of PKC. In parallel experiments, a change of PKC activity was observed. PMA rapidly decreased PKC activity in the cytosol of TSMCs, while increasing it transiently in the cell membranes within 30 min. Thereafter the membrane-associated PKC activity decreased and persisted for at least 24 h of PMA treatment. Moreover, treatment with 1 microM PMA for 2 and 24 h did not significantly change the KD and Bmax of the BK receptor for [H]BK binding (control: KD = 2.3 +/- 0.3 nM, Bmax = 25.2 +/- 1.4 fmol/mg protein). These results suggest that activation of PKC inhibit IP3 accumulation and consequently attenuate [Ca2+]i increase or inhibit independently both responses. The PMA-induced inhibition of responses to BK was associated with an increase in membranous PKC activity.

Inhibitory Effect of Phorbol Ester on Carbachol-Induced Signal Transduction in Cultured Canine Tracheal Smooth Muscle Cells

Regulation of the increases in inositol 1,4,5-trisphosphate (IP(3)) production and intracellular Ca(2+) concentration ([Ca(2+)](i)) by activation of protein kinase C (PKC) was investigated in cultured canine tracheal smooth muscle cells (TSMCs). Stimulation of TSMCs by carbachol led to IP(3) formation and caused an initial transient peak of [Ca(2+)](i) followed by a sustained elevation in a concentration-dependent manner. Pretreatment of TSMCs with phorbol 12-myristate 13-acetate (PMA, 1 &mgr;M) for 30 min blocked the carbachol-induced IP(3) formation and Ca(2+) mobilization. Following preincubation, carbachol-induced Ca(2+) mobilization recovered within 24 h. The concentrations of PMA that gave half-maximal inhibition of carbachol-induced IP(3) formation and increase in [Ca(2+)](i) were 7 and 4 nM, respectively. Prior treatment of TSMCs with staurosporine (1 &mgr;M), a PKC inhibitor, inhibited the ability of PMA to attenuate carbachol-induced responses. Inactive phorbol ester, 4alpha-phorbol 12,13-didecanoate at 1 &mgr;M, did not inhibit these responses to carbachol. The K(d) and B(max) of the muscarinic receptor for [(3)H]N-methylscopolamine binding were not significantly changed by PMA treatment. PMA also decreased PKC activity in the cytosol of TSMCs, while increasing it transiently in the membranes within 30 min. Thereafter, the membrane-associated PKC activity decreased and persisted for at least 24 h of PMA treatment. Taken together, these results suggest that activation of PKC may inhibit phosphoinositide hydrolysis and consequently attenuate the [Ca(2+)](i) increase or inhibit both responses independently. The inhibition by PMA of carbachol-induced responses was inversely correlated with membranous PKC activity. Copyright 1995 S. Karger AG, Basel

Effect of phorbol ester on phosphoinositide hydrolysis and calcium mobilization induced by endothelin-1 in cultured canine tracheal smooth muscle cells

Regulation of the increase in inositol 1,4,5-trisphosphate (IP3) production and intracellular Ca2+ concentration ([Ca2+]i) by protein kinase C (PKC) was investigated in cultured canine tracheal smooth muscle cells (TSMCs). Stimulation of TSMCs by endothelin-1 (ET-1) led to IP3 formation and caused an initial transient peak followed by a sustained elevation of [Ca2+]i in a concentration-dependent manner. Pretreatment of TSMCs with phorbol 12-myristate 13-acetate (PMA, 1 microM) for 30 min blocked the ET-1-induced IP3 formation and Ca2+ mobilization. However, this inhibition was reduced after incubating the cells for 8 h with PMA. Following preincubation, ET-1-induced Ca2+ mobilization recovered with time and reached the same extent of control cells within 48 h. The concentrations of PMA that gave half-maximal inhibition (-logEC50) of ET-1-induced IP3 formation and increase in [Ca2+]i were 8.6 and 8.4 M, respectively. Prior treatment of TSMCs with staurosporine (1 microM), a PKC inhibitor, inhibited the ability of PMA to attenuate ET-1-induced responses, suggesting that the inhibitory effect of PMA is mediated through the activation of PKC. In parallel with the effect of PMA on the ET-1-induced IP3 formation and Ca2+ mobilization, a change of PKC activity was observed in TSMCs. PMA rapidly decreased PKC activity in the cytosol of TSMCs, while increasing it transiently in the membranes within 30 min. Thereafter the membrane-associated PKC activity decreased and persisted for at least 24 h of PMA treatment. Taken together, these results suggest that activation of PKC may inhibit the phosphoinositide hydrolysis and consequently attenuate the [Ca2+]i increase or inhibit independently both responses. The PMA-induced inhibition of responses to ET-1 was associated with an increase in membranous PKC activity.

Sarafotoxin-induced calcium mobilization in cultured dog tracheal smooth muscle cells

Sarafotoxin b (S6b)-induced changes in intracellular Ca2+ concentration ([Ca2+]i) were monitored in cultured canine tracheal smooth muscle cells (TSMCs) by a fluorescent Ca2+ indicator fura-2. S6b elicited an initial transient peak followed by a sustained elevation of [Ca2+]i. BQ-123, an endothelin-A (ETA) receptor antagonist, had a high affinity to block the rise in [Ca2+]i response to S6b. In the absence of external Ca2+, only an initial transient peak of [Ca2+]i was seen, the sustained elevation of [Ca2+]i could then be evoked by addition of 1.8 mM Ca2+. Ca2+ influx was required for the changes of [Ca2+]i, since the Ca(2+)-channel blockers, diltiazem, verapamil, and Ni2+, decreased both the initial and sustained elevation of [Ca2+]i in response to S6b. TSMCs pretreated with phorbol 12-myristate 13-acetate (PMA, 1 microM) for 30 min attenuated Ca2+ mobilization induced by S6b, which was reversed by staurosporine, a protein kinase C (PKC) inhibitor. The change of [Ca2+]i induced by S6b was attenuated by cholera toxin pretreatment, but not by pertussis toxin. These data demonstrate that the initial detectable increase in [Ca2+]i stimulated by S6b is due to the activation of ETA receptors and subsequent release of Ca2+ from internal stores, whereas the contribution of external Ca2+ follows and partially involves a diltiazem- and verapamil-sensitive process. The inhibition of PMA on S6b-induced Ca2+ mobilization was inversely correlated with membraneous PKC activity.

5-Hydroxytryptamine-stimulated calcium mobilization in cultured canine tracheal smooth muscle cells

5-Hydroxytryptamine (5-HT)-induced increase of intracellular Ca2+ concentration ([Ca2+]i) was monitored in cultured canine tracheal smooth muscle cells (TSMCs) using a fluorescent Ca2+ indicator Fura-2. Stimulation of TSMCs by 5-HT produced an initial transient peak followed by a sustained, concentration-dependent elevation of [Ca2+]i. The log (EC50) values of 5-HT for the peak and sustained plateau responses were -7.43 and -7.60 M, respectively. 5-HT1A and 5-HT3 receptor antagonists, NAN-190 and metoclopramide, inhibited the 5-HT-stimulated increase in [Ca2+]i with pKB values of 6.3 and 6.2, respectively, indicating that the 5-HT receptors mediating Ca2+ signal had low affinity for these receptor antagonists. In contrast, 5-HT2A receptor antagonists, ketanserin and mianserin, had high affinity in antagonizing the changes in [Ca2+]i response to 5-HT with pKB values of 8.3 and 8.3, respectively. The sustained elevation of [Ca2+]i was dependent on the presence of extracellular Ca2+. Removal of extracellular Ca2+ by addition of 2 mM EGTA during the sustained phase caused a rapid decline in [Ca2+]i to the resting level. In the absence of extracellular Ca2+, only an initial peak was observed which then declined to the resting level; the sustained elevation of [Ca2+]i could then be evoked by addition of 1.8 mM Ca2+ in the continued presence of 5-HT. Ca2+ influx was required for the changes of [Ca2+]i, since the Ca(2+)-channel blockers, diltiazem, verapamil, and Ni2+, decreased both the initial and sustained elevation of [Ca2+]i in response to 5-HT. These Ca(2+)-channel blockers also decreased the sustained elevation of [Ca2+]i when applied during the plateau phase. In conclusion, these findings indicate that the initial increase in [Ca2+]i stimulated by 5-HT acting on 5-HT2A receptors is due to the release of Ca2+ from internal stores, followed by the influx of external Ca2+ into the cells. The influx of extracellular Ca2+ partially involves a diltiazem and verapamil sensitive Ca2+ channel.

Bradykinin-stimulated calcium mobilization in cultured canine tracheal smooth muscle cells

Bradykinin (BDK)-induced increases in intracellular Ca2+ concentration ([Ca2+]i) were monitored in cultured canine tracheal smooth muscle cells (TSMCs) using a fluorescent Ca2+ indicator, Fura-2. BDK and kallidin caused an initial transient peak followed by a sustained elevation of [Ca2+]i in a concentration-dependent manner, with half-maximal stimulation (log EC50) obtained at -8.10 M and -8.04 M, respectively. The BDK-induced rise in [Ca2+]i was not affected by the BDK B1 receptor antagonist, des-Arg9[Leu8]-BDK (10 microM). However, the BDK B2 receptor antagonists des-Arg[Hyp3, Thi5,8, D-Phe7]-BDK and Hoe 140 had high affinity in antagonizing BDK with pKB values of 7.5 +/- 0.3 and 8.7 +/- 0.3, respectively. The sustained phase of the rise in [Ca2+]i was dependent on the presence of external Ca2+, as evidenced by a decline to the resting level on addition of EGTA. In the absence of external Ca2+, only an initial transient peak was seen which then declined to the resting level; a sustained elevation of [Ca2+]i could then be evoked by addition of 1.8 mM Ca2+ in the continued presence of BDK. Ca2+ influx was required for the changes in [Ca2+]i, since Ca(2+)-channel blockers, diltiazem, verapamil, and Ni2+, decreased both the initial and sustained elevation of [Ca2+]i in response to BDK. In conclusion, these findings indicate that the initial increase in [Ca2+]i stimulated by BDK acting on BDK B2 receptors is due to the release of Ca2+ from internal stores, followed by the influx of external Ca2+ into the cells. The influx of extracellular Ca2+ partially involves a diltiazem- and verapamil-sensitive Ca2+ channel.

The effect of cyclic AMP elevating agents on bradykinin- and carbachol-induced signal transduction in canine cultured tracheal smooth muscle cells

1. The effects of cholera toxin (CTX), forskolin and dibutyryl cyclic AMP on bradykinin (BK)- and carbachol-induced accumulation of inositol phosphates (IPs) and Ca2+ mobilization were investigated in canine cultured tracheal smooth muscle cells (TSMCs). The BK-induced responses were mediated via a G protein which was not inhibited by CTX or pertussis toxin treatment. 2. BK-stimulated IPs accumulation and Ca2+ mobilization were potentiated by CTX (10 micrograms ml-1) pretreatment which was time-dependent. Maximal increase of these responses occurred after 24 h treatment with CTX. The concentration-effect relationship of BK-induced responses were shifted to the left and BK was substantially more effective in CTX-treated cells than in the control cells. This enhancing effect of CTX did not occur with carbachol. 3. Short-term (< 4 h) treatment with forskolin (10 microM) or dibutyryl cyclic AMP (1 mM) failed to accentuate BK-induced responses, but long-term (> 4 h) treatment of TSMCs with these agents mimicked the enhancing effect of CTX, suggesting that CTX-induced enhancement of BK responsiveness might be due to a rise in cyclic AMP. 4. Prolonged treatment of TSMCs with these agents was accompanied by an increase in cell surface [3H]-BK binding sites, which was inhibited by concurrent incubation with cycloheximide, an inhibitor of protein biosynthesis. Cycloheximide also abolished the potentiating actions of CTX, forskolin, and dibutyryl cyclic AMP on BK-induced IPs formation and Ca2+ mobilization. 5. The locus of this enhancement was further investigated by examining the effects of CTX, forskolin and dibutyryl cyclic AMP on A1F4(-)-induced IPs accumulation in canine TSMCs. AIF4-induced IPs accumulation was not affected by CTX, forskolin, or dibutyryl cyclic AMP treatment, supporting the contention that this stimulatory effect is located at the BK receptor level.6. These results demonstrate that the augmentation of BK-induced IPs accumulation and Ca2+mobilization produced by CTX, forskolin and dibutyryl cyclic AMP involves a cyclic AMP-dependent mechanism which is induced by a sustained increase in the level of intracellular cyclic AMP. CTX and forskolin may promote an increase of the synthesis of BK receptors, and thereby enhance BK-induced responses.

Calcium mobilization induced by endothelins and sarafotoxin in cultured canine tracheal smooth muscle cells

Endothelins (ETs)- and sarafotoxin (S6b)-induced rises in intracellular Ca2+ concentration ([Ca2+]i) were monitored in cultured canine tracheal smooth muscle cells by using a fluorescent Ca2+ indicator fura-2. ET-1, ET-2, ET-3 and S6b elicited an initial transient peak and followed by a sustained elevation of [Ca2+]i, with half-maximal effect (EC50) of 18, 20, 38 and 21 nM, respectively. BQ-123, an ETA receptor antagonist, had a high affinity to block the rise in [Ca2+]i response to ET-1, ET-2, and S6b, as well as a low affinity for ET-3. Removal of external Ca2+ by addition of EGTA during the sustained phase, caused a rapid decline in [Ca2+]i to the resting level. In the absence of external Ca2+, only an initial transient peak of [Ca2+]i was seen, the sustained elevation of [Ca2+]i could then be evoked by addition of 1.8 mM Ca2+. Ca2+ influx was required for the changes of [Ca2+]i, since the Ca(2+)-channel blockers, diltiazem, verapamil, and Ni2+, decreased both the initial and sustained elevation of [Ca2+]i response to these peptides. ETs exhibited homologous desensitization of the Ca2+ response, but partial heterologous desensitization of the Ca2+ response mediated by carbachol to different extents. In contrast, ETs did not desensitize the Ca2+ response induced by ATP or vice versa. These data demonstrate that the initial detectable increase in [Ca2+]i stimulated by these peptides is due to the activation of ETA receptors and subsequently the release of Ca2+ from internal stores, whereas the contribution of external Ca2+ follows and partially involves a diltiazem- and verapamil-sensitive process.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of phorbol ester on phosphoinositide hydrolysis and calcium mobilization in cultured canine tracheal smooth muscle cells

In cultured canine tracheal smooth muscle cells (TSMCs), muscarinic receptor stimulation led to phosphoinositide (PI) hydrolysis, formation of inositol phosphates (IPs), and mobilization of intracellular Ca2+. Desensitization of IPs accumulation and Ca2+ mobilization evoked by carbachol was investigated using [3H]inositol labelling and Ca(2+)-sensitive dye fura-2. Treatment of TSMCs with phorbol 12-myristate 13-acetate (PMA) for 30 min blocked the carbachol-stimulated formation of IPs and mobilization of Ca2+. The concentrations of PMA that gave half-maximal and maximal inhibition of carbachol-induced IPs accumulation were 70 nM and 1 microM, respectively. The inhibitory effect of PMA on carbachol-induced responses was reversed by staurosporine, a protein kinase C (PKC) inhibitor, suggesting that the inhibitory effect of PMA was mediated through the activation of PKC. Treatment of TSMCs with PMA for 24 h, the cells remained the ability to response to carbachol-induced IPs accumulation and Ca2+ mobilization with the same extent as that observed in the control group. Inactive phorbol ester, 4 alpha-phorbol 12, 13-didecanoate at 1 microM, did not inhibit the responses. The KD and Bmax of the muscarinic receptor for [3H]N-methyl scopolamine binding were not significantly changed by PMA treatment for either 30 min or 24 h. The locus of this inhibition was further investigated by examining the effect of PMA on AlF4(-)-stimulated IPs accumulation in canine TSMCs. AlF4(-)-induced response was inhibited by PMA treatment, supporting that G protein(s) can be directly activated by AlF4- which was uncoupled to phospholipase C (PLC) by PMA treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Endothelin- and sarafotoxin-induced phosphoinositide hydrolysis in cultured canine tracheal smooth muscle cells

The endothelins (ETs) and sarafotoxin are two structurally related classes of potently contractile peptides. To understand the mechanism of action of ETs, we have examined the effect of ETs and sarafotoxin on phosphoinositide (PI) hydrolysis in cultured canine tracheal smooth muscle cells (TSMCs). ET-1, ET-2, ET-3, and sarafotoxin caused dose-dependent accumulation of inositol phosphatase (IPs) and tracheal smooth muscle contraction. BQ-123, an ETA receptor antagonist, had a high affinity to block the ET-1-induced IP accumulation and tracheal smooth muscle contraction with pKB values of 7.3 and 7.4, respectively. Pretreatment of TSMCs with cholera toxin impaired the ability of ET-1 and ET-2 to stimulate IP formation, whereas there was no effect by treatment with pertussis toxin. Stimulation of PI turnover by these peptides required the presence of extracellular Ca2+ and was blocked by treatment with EGTA. The addition of Ca2+ (3-620 nM) to digitonin-permeabilized TSMCs directly stimulated IP accumulation. A further Ca(2+)-dependent increase in IP formation was obtained by inclusion of either GTPrS or ET-1. The combined presence of GTPrS and ET-1 elicited an additive effect on IP formation. Short-term exposure to phorbol 12-myristate 13-acetate (PMA, 1 microM) abolished the stimulation of PI hydrolysis induced by these peptides. The inhibitory effect of PMA on ET-induced response was reversed by staurosporine, a protein kinase C (PKC) inhibitor, suggesting that the inhibitory effect of PMA is mediated through the activation of PKC. Prolonged incubation of TSMCs with PMA resulted in a recovery of receptor responsiveness that may be due to downregulation of PKC.(ABSTRACT TRUNCATED AT 250 WORDS)

5-Hydroxytryptamine receptor-mediated phosphoinositide hydrolysis in canine cultured tracheal smooth muscle cells

1. 5-Hydroxytryptamine (5-HT) has been shown to induce contraction of tracheal smooth muscle. However, the mechanisms of action of 5-HT are not known. We therefore investigated the effects of 5-HT on phospholipase C (PLC)-mediated phosphoinositide (PI) hydrolysis and its regulation in canine cultured tracheal smooth muscle cells (TSMCs) labelled with [3H]-inositol. 5-HT-induced inositol phosphates (IPs) accumulation was time- and dose-dependent with a half-maximal response (EC50) and a maximal response at 0.38 +/- 0.05 and 10 microM, respectively. 2. Ketanserin and mianserin (10 and 100 nM), 5-HT2 receptor antagonists, were equipotent in blocking the 5-HT-induced IPs accumulation with pKB values of 8.46 and 8.21, respectively. In contrast, the dose-response curves of 5-HT-induced IPs accumulation were not shifted until the concentrations of NAN-190 and metoclopramide (5-HT1A and 5-HT3 receptor antagonists, respectively) were increased up to 10 microM. 3. Pretreatment of TSMCs with pertussis toxin or cholera toxin did not inhibit the 5-HT-induced IPs accumulation, but partially inhibited the AlF(4-)-induced IPs response. 4. Stimulation of IPs accumulation by 5-HT required the presence of external Ca2+ and was blocked by EGTA. The addition of Ca2+ (3-620 nM) to digitonin-permeabilized TSMCs directly stimulated IPs accumulation. A further Ca(2+)-dependent increase in IPs accumulation was obtained by inclusion of either guanosine 5'-O-(3-thiotriphoshate) (GTP gamma S) or 5-HT. The combination of GTP gamma S and 5-HT elicited an additive effect on IPs accumulation. 5. Treatment with phorbol 12-myristate 13-acetate (PMA, 1 microM, 30 min) abolished the 5-HT-induced IPs accumulation. The concentrations of PMA that gave a half-maximal and maximal inhibition of 5-HT-induced IPs accumulation were 2.2 +/- 0.4 nM and 1 microM, n = 3, respectively. The protein kinase C (PKC) activator, 4 alpha-phorbol 12,13-didecanoate, at 1 microM, did not influence this response. The inhibitory effect of PMA was reversed by staurosporine, a PKC inhibitor, suggesting that the inhibitory effect of PMA is mediated through the activation of PKC. 6. The site of this inhibition was further investigated by examining the effect of PMA on AlF(4-)-induced IPs accumulation in canine TSMCs. AlF(4-)-stimulated IPs accumulation was inhibited by PMA treatment, suggesting that the effect of PMA is distal to the 5-HT receptor. 7. Acetylcholine-induced IPs accumulation was completely inhibited by atropine, but not affected by ketanserin or mianserin, suggesting that 5-HT-induced IPs accumulation is not due to release of acetylcholine.8. These results demonstrate that 5-HT directly stimulates PLC-mediated PI hydrolysis via a pertussis toxin- and cholera toxin-insensitive GTP binding protein in canine TSMCs and that this coupling process is negatively regulated by PKC. 5-HT2 receptors may be predominantly mediating IPs accumulation and presumably IP-induced Ca2+ release may function as the transducing mechanism for 5-HT stimulated contraction of tracheal smooth muscle.

Bradykinin-stimulated phosphoinositide metabolism in cultured canine tracheal smooth muscle cells

1. Stimulation of bradykinin (BK) receptors coupled to phosphoinositide (PI) hydrolysis was investigated in canine cultured tracheal smooth muscle cells (TSMCs). BK, kallidin, and des-Arg9-BK, stimulated [3H]-inositol phosphates (IPs) accumulation in a dose-dependent manner with half-maximal responses (EC50) at 20 +/- 5, 13 +/- 4, and 2.3 +/- 0.7 nM, (n = 5), respectively. 2. D-Arg[Hyp3, D-Phe7]-BK and D-Arg[Hyp3, Thi5,8, D-Phe7]-BK, B2 receptor antagonists, were equipotent in blocking the BK-induced IPs accumulation with pKB = 7.1 and 7.3, respectively. 3. Short-term exposure of TSMCs to phorbol 12-myristate 13-acetate (PMA, 1 microM) attenuated BK-stimulated IPs accumulation. The concentrations of PMA that gave half-maximal and maximal inhibition of BK-induced IPs accumulation were 15 +/- 4 nM and 1 microM, n = 3, respectively. The inhibitory effect of PMA on BK-induced response was reversed by staurosporine, a protein kinase C (PKC) inhibitor, suggesting that the inhibitory effect of PMA was mediated through the activation of PKC. 4. Prolonged incubation of TSMCs with PMA for 24 h, resulted in a recovery of receptor responsiveness which may be due to down-regulation of PKC. The inactive phorbol ester, 4 alpha-phorbol 12, 13-didecanoate at 1 microM, did not inhibit this response. 5. The site of this inhibition was further investigated by examining the effect of PMA on AlF(4-)-induced IPs accumulation in canine TSMCs. AlF(4-)-stimulated IPs accumulation was inhibited by PMA treatment, suggesting that the G protein(s) can be directly activated by AlF4-, which is uncoupled from phospholipase C by PMA treatment. 6. Incubation of TSMCs in the absence of external Ca2+ or upon removal of Ca2+ by addition of EGTA, caused a decrease in IPs accumulation without changing the basal levels. Addition of Ca2+ (3-620 nM) to digitonin-permeabilized TSMCs stimulated IPs accumulation was obtained by inclusion of either guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) or BK. The combination of GTP gamma S and BK caused an additive effect on IPs accumulation.7. Pretreatment of TSMCs with cholera toxin enhanced BK-stimulated IPs accumulation, whereas there was no effect with pertussis toxin.8. These data suggest that BK-stimulated PI metabolism is mediated by the activation of BK B2 receptors coupling to a G protein which is not blocked by cholera toxin or pertussis toxin treatment and dependent on external Ca2+. The transduction mechanism of BK coupled to PI hydrolysis is sensitive to feedback regulation by PKC.

Muscarinic regulation of cytosolic free calcium in canine tracheal smooth muscle cells: Ca2+ requirement for phospholipase C activation

1. The relationship between muscarinic receptor-mediated phosphatidylinositol 4,5-bisphosphate (PIP2) breakdown and the increase of intracellular Ca2+ ([Ca2+])i has been examined in canine cultured tracheal smooth muscle cells (TSMCs). 2. Addition of acetylcholine (ACh) and carbachol led to a 2-3 fold increase in [Ca2+]i over the resting level as determined by fura-2, with half-maximal stimulation (EC50) obtained at concentrations of 97 and 340 nM, respectively. Addition of the partial agonist, bethanechol, showed a smaller increase in PIP2 turnover and [Ca2+]i than did ACh or carbachol. 3. Addition of ACh or carbachol to TSMCs that had been prelabelled with [3H]-inositol led to the rapid (5-15 s) release of inositol mono, bis and trisphosphates IP1, IP2 and IP3. The time course of IP3 accumulation is correlated with the time course of the peak rise in [Ca2+]i. 4. Inclusion of EGTA lowered the resting [Ca2+]i and markedly reduced the extent of the agonist-induced rise in [Ca2+]i. When assayed under conditions similar to those used for the [Ca2+]i measurements, EGTA reduced the muscarinic agonist-stimulated inositol phosphates (IPs) accumulation. Conversely, ionomycin could stimulate IPs accumulation and elevate [Ca2+]i. The addition of Ca2+ (2.7-617 nM) to digitonin-permeabilized TSMCs directly stimulated IPs accumulation. 5. Both Ca2+ and guanosine-5'-O-(3-thiotriphosphate) (GTP gamma S) stimulated the formation of IPs in digitonin-permeabilized TSMCs prelabelled with [3H]-inositol. A further calcium-dependent increase in IPs accumulation was obtained by inclusion of either GTP gamma S or carbachol. The combined presence of carbachol and GTP gamma S elicited a synergistic effect on IPs accumulation, with half-maximal stimulation observed at approximately 8 nM free Ca2+.6. These results indicate that (i) the magnitude of the initial rise in [Ca2+], is directly related to the production of IPs and (ii) the phospholipase C-mediated PIP2 breakdown in TSMCs is sensitive to regulation by physiologically relevant concentrations of free Ca2+ ([Ca2+]f).

Acute respiratory failure due to Pneumocystis carinii pneumonia

Pneumonia caused by Pneumocystis carinii is the most frequent indication for admission of AIDS patients to intensive care units. In this article, an approach to the diagnosis and management of this condition will be presented along with prognostic information. Differential diagnosis will be discussed, and characteristic responses to current standard and alternative chemotherapeutic agents and modes of ventilatory support will be reviewed.

A computerised out-patient medical records programme based on the Summary Time-Oriented Record (STOR) System

Advances in microcomputer hardware and software technology have made computerised outpatient medical records practical. We have developed a programme based on the Summary Time-Oriented Record (STOR) system which complements existing paper-based record keeping. The elements of the Problem Oriented Medical Record (POMR) System are displayed in two windows within one screen, namely, the SOAP (Subjective information, Objective information, Assessments and Plans) elements in the Reason For Encounter (RFE) window and the problem list with outcomes in the Problem List (PL) window. Context sensitive child windows display details of plans of management in the RFE window and clinical notes in the PL window. The benefits of such innovations to clinical decision making and practice based research and its medico-legal implications are discussed.

The predictive value of the time course of ST segment depression during exercise testing in patients referred for coronary angiograms

We studied the time course of ST segment depression during and after exercise testing in 462 subjects who also had coronary angiograms. Sixty-three percent of patients with late onset-early offset ST depression, previously reported to be likely to have false positive tests, had significant coronary artery disease, and 32% had three-vessel disease. Those with early onset and late offset ST depression and those with resting ST depression that was accentuated with exercise had a high prevalence of significant coronary artery disease and three-vessel disease. We found that observation of the time course of ST depression during and after exercise adds significantly to the information gained during exercise testing.

Binding of platelet activating factor by isolated membranes from U937 cells

Platelet activating factor (PAF), 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (1-O-alkyl-2-acetyl-GPC) has been known to have biological effect on cells. The mechanisms of the effect of the potent phospholipid on cells has not been established. We have used 1-O-[3H]alkyl-2-acetyl-GPC [( 3H]PAF) to study the interaction on the isolated membranes of U937 cells. The binding process was time, protein concentration, temperature dependent and reversible. The binding of [3H]PAF to the U937 cell membranes was slightly inhibited by the addition of PAF analogue, 3-O-Hexadecyl-2-acetyl-sn-glycerol-1-phosphorylcholine. U937 cell membranes showed high affinity binding sites for PAF with equilibrium dissociation constant (Kd) of 5 x 10(-9) M. The displacement of bound [3H]PAF with 500-fold excess of nonlabeled PAF was not altered suggesting that the bound [3H]PAF was not degraded during the binding. Binding of [3H]PAF on U937 cell membranes was inhibited by PAF antagonist, 59227RP. The kinetic of the inhibition by PAF antagonist is competitive suggesting that PAF and PAF antagonist bind at the same site.

Tumor trapping of 5-fluorouracil: in vivo 19F NMR spectroscopic pharmacokinetics in tumor-bearing humans and rabbits

The pharmacokinetics of 5-fluorouracil (5FU) were studied in vivo in patients with discrete tumors and in rabbits bearing VX2 tumors by using 19F NMR spectroscopy. The human studies were conducted in a 1.5-T Magnetom magnetic resonance imager (Siemens), and the rabbit studies were conducted in a 4.7-T GE/Nicolet 33-cm bore magnet. Free 5FU was detected in the tumors of four of the six patients and in all VX2 tumors but not in normal rabbit tissues. No other metabolites were seen in these tumors, contrary to the extensive catabolism we had previously documented using 19F NMR spectroscopy in both human and animal livers. The tumor pool of free 5FU in those human tumors that trapped 5FU was determined to have a half-life of 0.4-2.1 hr, much longer than expected and significantly longer than the half-life of 5FU in blood (5-15 min), whereas the half-life of trapped 5FU in the VX2 tumors ranged from 1.05 to 1.22 hr. In this initial experience, patient response to chemotherapy may correlate with extent of trapping free 5FU in the human tumors. These studies document that NMR spectroscopy is clinically feasible in vivo, allows noninvasive pharmacokinetic analyses at a drug-target tissue in real time, and may produce therapeutically important information at the time of drug administration. Demonstration of the trapping of 5FU in tumors provides both a model for studying metabolic modulation in experimental tumors (in animals) and a method for testing modulation strategies clinically (in patients).

Direct enzyme linked antiglobulin tests (ELAT) for detecting in-vivo sensitized erythrocytes: evaluation of screening for ABO incompatibility of newborn

ABO incompatibility of the newborn is one instance where immune hemolysis may present with a negative direct antiglobulin test (DAT) and therefore a simple sensitive test for detecting sensitization would be useful in this clinical situation. To evaluate the usefulness of ELAT in detecting in-vivo sensitized red cells, 1608 maternal-baby pairs were screened for ABO incompatibility over a period of 10 mth. Of 251 ABO-incompatible babies, there were 49 (19.5%) with positive DAT, but an additional 67 (26.7%) were ELAT positive. These were eluate positive as well, indicating that the increased number with sensitized cells as shown by ELAT is due to detection of in-vivo sensitized cells. The positive predictive value for ABO hemolytic disease of the newborn (HDN) is 48%, which is two times that of DAT. Calculating the difference of the absorbance from baseline (delta OD) may give an indication of degree of sensitization which together with the maternal antibody titre would aid us in the estimation of antigen dosage on the baby's red cells and in the appraisal of the role of antigen dosage in HDN.

Haematolytic disease due to ABO incompatibility: incidence and value of screening in an Asian population

The population in Singapore is predominantly Asian, with Chinese forming the major ethnic group. The incidence of haemolytic disease of the newborn (HDN) due to Rh incompatibility is very low. The true incidence of HDN due to ABO incompatibility is unknown. Early discharge is practised in Singapore making it important to predict severe HDN due to ABO incompatibility as this would constitute the main cause of haemolysis next to G6PD deficiency. One thousand, six hundred and eight baby-maternal pairs were typed for ABO, Rh, and tested for direct Coombs' test, maternal titre, cord bilirubin and haptoglobin levels. Two hundred and fifty-one were found to be ABO incompatible, with 141 group A and 110 group B babies. The incidence of HDN due to ABO incompatibility was 3.7% of all group O mothers. Coombs' test, maternal antibody titre, cord bilirubin and haptoglobin levels were of low predictive value for severe HDN due to ABO incompatibility. The data further support the notion that it is not cost effective to screen for ABO incompatibility.

Parameningeal rhabdomyosarcoma (including the orbit): results of orbital irradiation

Twenty-three patients with parameningeal (including orbital rhabdomyosarcoma (RMS)) were treated at Memorial Sloan-Kettering Cancer Center (MSKCC) between July 1971 and January 1983. Twenty were children with a mean age of 6 and 3 were adults. In 6 patients, the primary tumor was from the orbit, whereas the remaining 17 had other parameningeal primary sites. The tumors were in a very progressive local stage, with extensive destruction of the facial bones in 19 patients. Eight patients were treated with T2 chemotherapy protocol and 15 received T6. Seven patients received 5,000 to 7,200 rad delivered to the primary tumor in 11-16 weeks, 15 patients received between 4,500 to 5,000 rad in 4-7 weeks, and 1 patient received 3,000 rad in 3 weeks for residual microscopic disease following surgery. Two patients were treated with radiation to the whole brain; no patients received radiation of the whole central nervous axis (CNA). Fifteen of the 23 patients (65%) are alive and well with a medical follow-up time of 5 years. Two patients died of therapeutic complications and six died of tumor spread. In five patients, involvement of the central nervous system (CNS) was the cause of death. The prognosis of orbital RMS with parameningeal involvement is no better than in other tumors of parameningeal sites. In those patients who had impaired vision because of optic nerve damage prior to treatment, the vision did not improve following treatment. There was no impaired vision seen due to radiation damage of eye structures except in the lens.

Generation of biologically active, complement-(C5) derived peptides by cathepsin H

The thiol proteinase cathepsin H, isolated and purified from rat liver lysosomes, provokes acute inflammation characterized by the accumulation of polymorphonuclear leukocytes (PMN) when injected intracutaneously into newborn rats. We have examined the possibility that the accumulation of PMN at skin sites injected with cathepsin H is due, in part, to generation locally of C-derived chemotactic factors. We have found that cathepsin H acts in a concentration- and time-dependent fashion in whole human (and rat) EDTA-plasma to generate C5-derived peptides with chemotactic activity for PMN. Chemotactic activity was not generated in EDTA-plasma by either heat-inactivated cathepsin H or by a combination of active enzyme and a thiol proteinase inhibitor isolated from rat epidermis. Cathepsin H also acted in a concentration- and time-dependent fashion on isolated (functionally pure) human C5 to yield chemotactic activity for PMN as well as PMN lysosomal enzyme-releasing activity. Whereas 10 ng/ml cathepsin H generated significant chemotactic activity from isolated C5 (1000 CH50 U/ml), 7 to 10 micrograms/ml were required to generate chemotactic activity in whole EDTA-plasma. Cathepsin H not only was capable of generating biologically active, C5-derived peptides, but also was capable of degrading these peptides. Incubation of either whole EDTA-plasma or isolated C5 with high concentrations of cathepsin H (e.g., 25 micrograms/ml and 100 ng/ml, respectively) caused the rapid appearance of chemotactic activity followed by an equally rapid disappearance. PMN accumulated more rapidly in the skin of newborn rats injected with cathepsin H-treated C5 than in the skin of animals injected with cathepsin H alone. These data suggest that generation by cathepsin H of C-derived chemotactic activity contributes to the ability of this enzyme to induce dermal inflammation.

Generation of biologically active, complement-(C5) derived peptides by cathepsin H

The thiol proteinase cathepsin H, isolated and purified from rat liver lysosomes, provokes acute inflammation characterized by the accumulation of polymorphonuclear leukocytes (PMN) when injected intracutaneously into newborn rats. We have examined the possibility that the accumulation of PMN at skin sites injected with cathepsin H is due, in part, to generation locally of C-derived chemotactic factors. We have found that cathepsin H acts in a concentration- and time-dependent fashion in whole human (and rat) EDTA-plasma to generate C5-derived peptides with chemotactic activity for PMN. Chemotactic activity was not generated in EDTA-plasma by either heat-inactivated cathepsin H or by a combination of active enzyme and a thiol proteinase inhibitor isolated from rat epidermis. Cathepsin H also acted in a concentration- and time-dependent fashion on isolated (functionally pure) human C5 to yield chemotactic activity for PMN as well as PMN lysosomal enzyme-releasing activity. Whereas 10 ng/ml cathepsin H generated significant chemotactic activity from isolated C5 (1000 CH50 U/ml), 7 to 10 micrograms/ml were required to generate chemotactic activity in whole EDTA-plasma. Cathepsin H not only was capable of generating biologically active, C5-derived peptides, but also was capable of degrading these peptides. Incubation of either whole EDTA-plasma or isolated C5 with high concentrations of cathepsin H (e.g., 25 micrograms/ml and 100 ng/ml, respectively) caused the rapid appearance of chemotactic activity followed by an equally rapid disappearance. PMN accumulated more rapidly in the skin of newborn rats injected with cathepsin H-treated C5 than in the skin of animals injected with cathepsin H alone. These data suggest that generation by cathepsin H of C-derived chemotactic activity contributes to the ability of this enzyme to induce dermal inflammation.

Radioimmunoelectrophoresis, a sensitive method for detecting cleavage of the fifth component of human complement (C5)

A method has been developed for detecting cleavage of human C5 in serum and whole blood as a consequence of complement activation. Standard, single-dimension immunoelectrophoresis was performed using as antibody a radioiodinated IgG fraction prepared from a commercially available antiserum to human C5. Autoradiographs developed after radioimmunoelectrophoresis of either normal human serum or functionally pure human C5 revealed only one precipitin band. In contrast, when either zymosan-treated serum or trypsin-treated human C5 were examined with this technique, two additional precipitin bands were detected. One migrated more anodally than native C5 while the other remained at the origin (cathode). Radioimmunoelectrophoresis was significantly more sensitive as an indicator of complement activation in human serum than either measurements of total hemolytic complement or a standard assay for complement (C5)-derived chemotactic activity.

Complement (C5)-derived chemotactic activity in serum from patients with pancreatitis

Samples of serum and plasma obtained from eight patients with acute pancreatitis were examined for the presence of complement-derived chemotactic activity for human PMN. Significant chemotactic activity was found in acute phase serum and plasma samples from five patients. The presence of chemotactic activity was associated with reduced levels of CH50 as well as degradation products of C5 (detected by a new method, i.e., radioimmunoelectrophoresis). The chemotactic activity was heat-stable (56 degrees C for 30 min), inhibitable by treatment with antibodies to human C5, and exhibited an apparent molecular weight of 16,000 (determined by chromatography on Sephadex G-75). These properties are identical with those of chemotactic C5-derived peptides (C5a and/or C5a des Arg). Recently, C5-derived peptides have been implicated as being mediators of acute lung injury (i.e., "shock lung") in some clinical situations. It is intriguing to speculate, therefore, that circulating C5-derived chemotactic peptides may play a role in the pathogenesis of the lung injury observed in some patients during the course of acute pancreatitis.

Wheat germ agglutinin specifically inhibits formyl peptide-induced polymorphonuclear leukocyte chemotaxis

Evidence that surface membrane glycoproteins of polymorphonuclear leukocytes (PMN) are involved in stimulus-response coupling prompted us to examine effects on these cells of various plant lectins. We have found that wheat germ agglutinin (WGA) (1.0 microgram/ml) completely, specifically, and irreversibly inhibits directed migration (chemotaxis) of human PMN toward the synthetic peptide, N-formylmethionyl-leucyl-phenylalanine (FMLP) (0.1 to 100 nM). This effect of WGA was not shared by subagglutinating concentrations of either concanavalin A or Bandeirea simplicifolia lectin. In contrast to its effects on FMLP-induced chemotaxis, WGA did not influence other FMLP-induced PMN responses (i.e., selective discharge of lysosomal enzymes from cytochalasin B-treated cells, generation of superoxide anion radical(s). WGA also did not influence PMN chemotactic responses to either the complement-derived peptide, C5a, or the lipoxygenase product, leukotriene B4. Inhibition of FMLP-induced chemotaxis by WGA was not reversed by washing WGA-treated cells, but was reversed (and prevented) by N-acetyl-D-glucosamine (not by N-acetyl-D-galactosamine or mannosamine). WGA did not affect either orientation or stimulated random motility of PMN, and did not interfere with specific binding to PMN of (3H)-FMLP. A derivative of WGA with 10-fold less agglutinating activity for human erythrocytes was prepared by treating the native lectin with cyanogen bromide and formic acid. The derivative also inhibited FMLP-induced PMN chemotaxis specifically and selectively. These data suggest that WGA specifically inhibits FMLP-induced PMN chemotaxis by attaching to N-acetyl-D-glucosamine residues at a locus on the PMN plasma membrane that is distinct from the binding site of the FMLP receptor.

Wheat germ agglutinin specifically inhibits formyl peptide-induced polymorphonuclear leukocyte chemotaxis

Evidence that surface membrane glycoproteins of polymorphonuclear leukocytes (PMN) are involved in stimulus-response coupling prompted us to examine effects on these cells of various plant lectins. We have found that wheat germ agglutinin (WGA) (1.0 microgram/ml) completely, specifically, and irreversibly inhibits directed migration (chemotaxis) of human PMN toward the synthetic peptide, N-formylmethionyl-leucyl-phenylalanine (FMLP) (0.1 to 100 nM). This effect of WGA was not shared by subagglutinating concentrations of either concanavalin A or Bandeirea simplicifolia lectin. In contrast to its effects on FMLP-induced chemotaxis, WGA did not influence other FMLP-induced PMN responses (i.e., selective discharge of lysosomal enzymes from cytochalasin B-treated cells, generation of superoxide anion radical(s). WGA also did not influence PMN chemotactic responses to either the complement-derived peptide, C5a, or the lipoxygenase product, leukotriene B4. Inhibition of FMLP-induced chemotaxis by WGA was not reversed by washing WGA-treated cells, but was reversed (and prevented) by N-acetyl-D-glucosamine (not by N-acetyl-D-galactosamine or mannosamine). WGA did not affect either orientation or stimulated random motility of PMN, and did not interfere with specific binding to PMN of (3H)-FMLP. A derivative of WGA with 10-fold less agglutinating activity for human erythrocytes was prepared by treating the native lectin with cyanogen bromide and formic acid. The derivative also inhibited FMLP-induced PMN chemotaxis specifically and selectively. These data suggest that WGA specifically inhibits FMLP-induced PMN chemotaxis by attaching to N-acetyl-D-glucosamine residues at a locus on the PMN plasma membrane that is distinct from the binding site of the FMLP receptor.